DC to DC charger - not needed for boats with proper alternators.

[newhaul]

Originally Posted by Fuss

I’m running Eve LF280K, 560ah 24v, I wouldn’t run battleborn as I have restricted space and Eve lf280k fits to within the mm.
The BMV712 says 150ah…often for an extended period, like 5 hours on occasion but generally over an hour.
150ah is 150ah unless the 712 lies…130-140 degrees is the temp that the alternator runs at after it stabilises …but measured from one of the bolts on the outside then probably 110 degrees C.

Ok so you are running a Daly 200amp single in and out .
https://lifepo.de/en/products/24v-56...th-eve-grade-a
That bms has Bluetooth connectabiljty and adjusting for current in and out. Perhaps it's set to 150 amp in for charging.

[Fuss]

Originally Posted by newhaul

Ok so you are running a Daly 200amp single in and out .
https://lifepo.de/en/products/24v-56...th-eve-grade-a
That bms has Bluetooth connectabiljty and adjusting for current in and out. Perhaps it's set to 150 amp in for charging.

But then the bmv712 would say 100 and not 150 and as it says 150, then it’s not likely that it’s limited to 100.

[newhaul]

Originally Posted by Fuss

But then the bmv712 would say 100 and not 150 and as it says 150, then it’s not likely that it’s limited to 100.

Again confusing amps with amp hours
Amps is instantaneous amp hours is capacity over time

[Fuss]

Originally Posted by newhaul

Again confusing amps with amp hours
Amps is instantaneous amp hours is capacity over time

I guess at this point, I should say that the BMV712 is not my first battery monitor and before that I had a bmv700, I think it was called, and before that another bmv something for 15 years.
So , just for info, I really don’t care much for the AH screen compared to the A screen. I like the A screen because when this reads - 20, I know that 20 Á‘s are coming out and when this screen reads 150, then I know that 150 A‘s are going in and so that if the battery is at 40% depth of discharge that roughly 2 and a bit hours later, the battery will be full again.

[Fuss]

Oops, I mean 60% dod, but hey, no-ones perfect right…

[sailorboy1]

At the heart of this is how long can an alternator 0ut out its max before it burns up. So how long is that? Is it 1 hour, 2 hours, 3 hours? I bet that once it has run at max even 1 hour it probably is has hot as it is going to get. And I bet a lot of that depends on the engine compart/enclosure. I know that if I open my enclosure and watch my regulator cycle through that alternator temperature drops a good amount. So if my enclosure had better air flow I probably could at max output forever.

I know Neal Calder wrote an article that showed the same using better ventilation.

This doesn't apply to me as I have my temperature setting and output turned down as I am not intetested in pushing my luck. There is only 1 way to find out if your installation can run at max output for hours and that is to risk it. He it works for you great and if not then it is only money.

[Simi 60]

Originally Posted by sailorboy1

At the heart of this is how long can an alternator 0ut out its max before it burns up. So how long is that? Is it 1 hour, 2 hours, 3 hours? I bet that once it has run at max even 1 hour it probably is has hot as it is going to get. And I bet a lot of that depends on the engine compart/enclosure. I know that if I open my enclosure and watch my regulator cycle through that alternator temperature drops a good amount. So if my enclosure had better air flow I probably could at max output forever.

I know Neal Calder wrote an article that showed the same using better ventilation.

This doesn't apply to me as I have my temperature setting and output turned down as I am not intetested in pushing my luck. There is only 1 way to find out if your installation can run at max output for hours and that is to risk it. He it works for you great and if not then it is only money.

Our ER is walk around sized well ventilated and have never ever seen it hotter in there than 38c after running engines all day.

Big frame alts still cooked when left to run full tits charging big AGM

Now on lifepo4 with 100 amp Delco 36si @ 24 v and 2 X sterling 35 amp @ dc2dc @ 24, the alt runs at between 58c at 1150rpm cruise and 63c at idle.

[CaptainRivet]

Originally Posted by Simi 60

Now on lifepo4 with 100 amp Delco 36si @ 24 v and 2 X sterling 35 amp @ dc2dc @ 24, the alt runs at between 58c at 1150rpm cruise and 63c at idle.

Which means you could put 20 or 30A DC2DC on, so the delco reaches 100c at idle. Still healthy but on the high side. Or if you regulate it externally you can run it till it reaches 90-95C, that's optimum amps for max lifespan. Bet you would see close to 100A from it then.
Delco seems to cope fine with your environment, 63C at idle with 70A draw of a 100A alternator is quite low.

[CaptainRivet]

Originally Posted by Fuss

I guess at this point, I should say that the BMV712 is not my first battery monitor and before that I had a bmv700, I think it was called, and before that another bmv something for 15 years.
So , just for info, I really don’t care much for the AH screen compared to the A screen. I like the A screen because when this reads - 20, I know that 20 Á‘s are coming out and when this screen reads 150, then I know that 150 A‘s are going in and so that if the battery is at 40% depth of discharge that roughly 2 and a bit hours later, the battery will be full again.

Did you measure the shunt and calibrated it properly? Use a clamp meter to check if current shown fits.
We slowly figuring out what you really have. As expected nothing magic.

[CaptainRivet]

Originally Posted by newhaul

Ok so you are running a Daly 200amp single in and out .
https://lifepo.de/en/products/24v-56...th-eve-grade-a
That bms has Bluetooth connectabiljty and adjusting for current in and out. Perhaps it's set to 150 amp in for charging.

Sounds logic

[Simi 60]

Originally Posted by CaptainRivet

Which means you could put 20 or 30A DC2DC on, so the delco reaches 100c at idle. Still healthy but on the high side.
<Snip>.
Delco seems to cope fine with your environment, 63C at idle with 70A draw of a 100A alternator is quite low.

Make your mind up
FYI, the 2nd one is the realty.

[Simi 60]

This morning before getting underway I added an additional cable from Alt+ to starter motor +
Original alt was 45 amp so figured cable likely too small for the 100 amp one.

Figured right, scored some extra amps from the dc2dc X 2
And temp at 1150rpm cruise stable at 65c for over an hour now.

[CaptainRivet]

Originally Posted by Simi 60

This morning before getting underway I added an additional cable from Alt+ to starter motor +
Original alt was 45 amp so figured cable likely too small for the 100 amp one.

Figured right, scored some extra amps from the dc2dc X 2
And temp at 1150rpm cruise stable at 65c for over an hour now.

Hope the added cable is same length and diameter then existing. How old is the existing one...
Suggest to use a clamp meter to check if current is equally splitted, if not suggest to replace old one too.
More current,more temps.
That's exactly what saved hundreds of alternators from burning when owners added drop in lifepo4.

[Simi 60]

Originally Posted by CaptainRivet

Hope the added cable is same length and diameter then existing.

It's same size and runs the same path so close enough to same length

How old is the existing one

Guessing as old as the engine

Suggest to use a clamp meter to check if current is equally splitted, if not suggest to replace old one too.

I'll just run to the shop and get some
Oh wait, we are actually out cruising full time - no shops out here

But I do intend on replacing it when we come out for maintenance at years end.

[CaptainRivet]

Originally Posted by Simi 60

It's same size and runs the same path so close enough to same length

Guessing as old as the engine

I'll just run to the shop and get some
Oh wait, we are actually out cruising full time - no shops out here

But I do intend on replacing it when we come out for maintenance at years end.

Just measure to see if you have a problem or not. You should be able to do this on achor, an engine room that has constant temp must be quite spacious.
Paralell cable must be same length, rough depends on length 20cm on 10m no problem, but on 2m it is. And the other cable is old so potentially much more resistance.
Hope you added postive and negative cable...